Direct Observation and Quantification of CO ₂ Binding Within an Amine-Functionalized Nanoporous Solid

TLDR

Understanding the molecular details of CO₂–sorbent interactions is critical for designing better carbon‑capture systems. We crystallographically resolved CO₂ molecules and their binding domains in an amine‑functionalized metal‑organic framework and modeled specific binding interactions, revealing substantial cooperative effects among guest molecules. Computational studies of sorption isotherms, heat of adsorption, and CO₂ lattice positions agree with crystallographic data, validating the simulations and showing that appropriate pore size, strongly interacting amine groups, and cooperative binding drive low‑pressure uptake and high capacity.

Abstract

Understanding the molecular details of CO(2)-sorbent interactions is critical for the design of better carbon-capture systems. Here we report crystallographic resolution of CO(2) molecules and their binding domains in a metal-organic framework functionalized with amine groups. Accompanying computational studies that modeled the gas sorption isotherms, high heat of adsorption, and CO(2) lattice positions showed high agreement on all three fronts. The modeling apportioned specific binding interactions for each CO(2) molecule, including substantial cooperative binding effects among the guest molecules. The validation of the capacity of such simulations to accurately model molecular-scale binding bodes well for the theory-aided development of amine-based CO(2) sorbents. The analysis shows that the combination of appropriate pore size, strongly interacting amine functional groups, and the cooperative binding of CO(2) guest molecules is responsible for the low-pressure binding and large uptake of CO(2) in this sorbent material.